The present invention relates to a tensioning device which is used to select and impart a moment of torque to an attached member such as a shaft, and which will bias the attached member to maintain contact between the attached member and a second member. The present torsional tensioning device has been found to be particularly useful in connection with conveyor belt cleaners which utilize scraper blades to clean the conveyor belt. Conveyor belt scraper blades are conventionally mounted on a shaft which is transverse to the direction of conveyor belt travel. When the shaft is rotated the blades are forced into contact with the belt to scrape off adherent material. Over time the scraper blades wear and lose contact with the belt thereby hampering the blades cleaning ability. The shaft on which the scraper blades are mounted must then be rotated to reposition the scraper blades against the belt.
Conveyor belt scraper blades are subjected to repeated impact forces which are generated by the blades coming into contact with conveyor belt splices and enlarged pieces of the conveyed material or debris which adheres to the belt, all of which can cause appreciable damage to the scraper blades or the conveyor mechanism. To promote effective cleaning of the conveyor belt and to avoid shutting the belt down for repair, it is of the utmost importance to provide the scraper blades with a shock absorbing capability.
Previous torsional tensioning devices of the types shown in U.S. Pat. Nos. 4,925,434 and 4,533,036 have been used in connection with conveyor belt scraper blades. In these devices the biasing means extends outward from the end of the conveyor belt cleaner shaft and away from the conveyor chute. Changes in length of the biasing means in these devices will affect the amount of clearance available on the outside of the conveyor mechanism along walkways and the like. These prior devices also leave the biasing means exposed, subjecting the biasing means to possible cutting or tearing from foreign objects. Torsional springs used for mounting a conveyor belt cleaner to a shaft are shown in U.S. Pat. Nos. 3,674,131 and 4,533,035. A torsion spring is also shown in U.S. Pat. No. 4,171,920.